The present invention relates to valves, pumps, and actuators and more particularly to electrically controlled valves or pumps in which a fluid passage is controlled by selectively blocking a fluid opening or moving a wall. Devices of this type have found wide use in pneumatic or fluid control systems and elsewhere.
In general, valves of this type may operate in relatively mild environments, for example where the controlled fluid is atmospheric air at low pressures, or in more challenging environments in which the fluid is a process fluid or gas that is reactive or exists at greater pressure, or in which the valve itself is to be mounted in an assembly subject to heat, vibration or other physical challenge.
In general, for air at low pressure in applications such as HVAC pressure or flow control, and for numerous other fluid pumping, switching or pneumatic control applications, the overall structure of the valve involves a manifold or a specially-shaped housing, and a structure that is actuated to control a valve opening. For this purpose, a cantilevered member that actuates in a bending mode may be well suited to size or geometrical constraints of the valve/pump housing. Such a bender may be made using piezoelectric material. By way of example, U.S. Pat. No. 5,460,202 of Hanley et al shows such a device wherein the actuator element is formed of a metal shim with piezoceramic sheets on both sides which are energized in opposite senses to cause the element to bend. In that device, the bender element is clamped, with an insulating plastic layer, between two blocks to fix one end, and a voltage is applied through solder-attached electrical leads to bend the actuator so that the distal, non-clamped end moves along a direction normal to the plane of the bender.
A drawback in bending actuators of this type is that the repetitive bending actuation can cause cracking. Furthermore solder-connection of the metal shim or of the leads for energizing the piezo plates can damage the piezo material and also result in localized stresses that may break the solder joint. Further, clamping of the bender end, introduction of mounting holes, and exposure to fluids may all damage the bender.
Accordingly a valve or pump with a more robust and easily mounted bender actuation assembly would be desirable.